Exploitation of Self-Sustaining Ontario Stream Populations of Brown Trout (Salmo trutta) and Brook Trout (Salvelinus fontinalis)

The August standing crop of harvestable brown trout (Salmo trutta, 90%), and brook trout (Salvelinus fontinalis, 9%) in the upper Sydenham River, Ont., was estimated at 499 trout/ha (63.2 kg/ha) during 1966 and 1967. Brown trout were of age I (68%), age II (23%), and the remainder of ages III, IV, V, and XIII. Brook trout were ages I (95%) and II only.The average annual harvest by 1501 anglers was 1135 fish (64% brown, 35% brook trout) at a rate of 0.34 fish/hr. Exploitation of the preseason standing populations of brown and brook trout was 23 and 59%, respectively. Catch per unit effort from the downriver section (all brown trout of ages II–IV and mean length of 34.0 cm) averaged 0.10 at an angling pressure of 264 hr/ha. An upriver section occupied predominantly (90%) by brown trout of age I–III and mean length of 26.8 cm yielded 0.67 trout/hr at an angling pressure of 251 hr/ha.The population structure, growth, and exploitation rate of naturalized brown trout favours its use in providing continuous angling of creditable quality in heavily fished headwater streams. Coexistence of self-sustaining populations of brown and brook trout provide a sustained, high-quality mixed fishery.